1. Field of the Invention
The present invention generally relates to devices for connecting optical waveguides, and more particularly to a push-pull, quick-release optical fiber connector which is compatible with ST-type connector receptacles.
2. Description of the Prior Art
The use of optical fibers for high speed communication and data transmission via optical signals has become well established. There are already hundreds of thousands of miles of optical fiber in use today. It has, therefore, become imperative to provide compatible optical fiber connectors which may easily be coupled and uncoupled, and a substantial development effort has been directed toward designing such connectors. As used herein, the term "connector" means an article which allows connection, disconnection and reconnection of two optical fibers, as opposed to a "splice," which normally connotes a permanent connection between the fibers.
Several optical fiber connector designs have incorporated a bayonet-style fastener, such as that shown in U.S. Pat. No. 3,803,409. In its simplest form, this type of fastener includes a coupling having one or more outwardly extending projections or lugs, and a rotatable, female socket having a spiral slot therein for receiving the lugs. The coupling may include an integral mounting plate for affixing the connector to a connection module, as shown in U.S. Pat. No. 3,947,182, or the coupling may comprise a double-ended receptacle which mates with two female sockets (one on each end of the fiber) as depicted in U.S. Pat. No. 3,948,582. A further improvement relates to the manner in which the female socket is rotated about the coupling. It was found that such rotation could result in undesirable grinding of the fiber end faces during the connection operation. To prevent such grinding, the connector body (ferrule) may be provided with means for aligning the ferrule with the connector receptacle, as suggested in U.S. Pat. Nos. 4,272,154, 4,354,731, and 4,793,683.
Such alignment means has been combined with a bayonet style fastener in U.S. Pat. No. 4,634,214. This connector is identified as an "ST" connector ("ST" is a trademark of American Telephone and Telegraph Co.), and an exemplary embodiment thereof is shown in FIG. 1. The prior art ST connector generally comprises a double-ended receptacle 1 which accommodates two plugs 2 (only one of which is depicted in FIG. 1) attached to the fiber ends. Each tubular end of receptacle 1 has a guide slot 3 which receives a guide stud 4 attached to the ferrule support of plug z; these elements prevent rotation of the ferrule with respect to the receptacle, which could otherwise damage the fiber end faces. Receptacle 1 also has diametrically opposed lugs 6 which slide into spiral or J-shaped slots 7 on the bayonet cap 8 of plug 2. Cap 8 is coupled to ferrule 5 in such a manner that cap 8 is free to rotate with respect to ferrule 5. An alignment sleeve (not shown) for the ferrules is also typically provided within receptacle 1. Additional features have been added to this basic ST design, such as the boot/cap extender shown in U.S. Pat. No. 4,812,009.
Although the ST connector is fairly simple to use, it still has several disadvantages. The first relates to the requirement that the cap 8 be manually rotated to effect the connection to receptacle 1. This precludes use of an ST connector in high density environments where there is insufficient room to manipulate cap s. The requirement of relative rotation between cap s and receptacle 1 also prevents ganging of connectors, i.e., the incorporation of multiple connectors into a single housing, such as the duplex fiber optic connectors illustrated in U.S. Pat. Nos. 4,762,388, 4,611,887, and 4,687,291, which are being installed in greater numbers for use in fiber distributed data integration (FDDI).
Instead of bayonet fastening, duplex connectors typically utilize latching mechanisms to engage the connector receptacles and plugs. Latch arms are also used to achieve a snap-lock in several simplex connector designs, including those disclosed in U.S. Pat. Nos. 4,225,214 and 4,240,695. Unfortunately, most of these designs still require manipulation of actuation arms to allow the latches to release, and therefore suffer from the same limitation as ST connectors regarding high density connection environments. One interesting latch design, however, overcomes this problem in a quick-release, push-pull type fiber optic connector. An example of such a connector is shown in U.S. Pat. No. 4,268,115. In this design, a slidable housing surrounds the connector plug body, the body having attached thereto and integral therewith two latches which engage an annular groove in the connector receptacle. When the housing slides over the connector body, away from the receptacle, two apertures in the housing contact the latch hooks and cause them to be released from the annular groove.
A similar push-pull fiber optic connector which is in wide use today is known as the "SC" connector, first manufactured by Nippon Telegraph and Telephone Co. (NTT) of Tokai, Japan. An exemplary embodiment of this connector is shown in FIG. 2. A more detailed description may be found in "Japanese Industrial Standard JIS C 5973 for F04-type optical fiber connectors," published by the Japanese Standards Association. This design also utilizes a double-ended receptacle 10, but both the receptacle and the plug 11 have a rectangular cross-section. Plug 11 includes a ferrule holder 12 which holds the ferrule 13. Ferrule holder 12 has notches 14 therein which engage with hooks 15 of latches 16 which are part of receptacle 10. Plug 11 further includes a slidable housing 17 surrounding ferrule holder 12. Housing 17 has slots 18 formed therein, which have side ramps 19 at their forward end. When plug 11 is inserted into receptacle 10, hooks 15 engage notches 14. Pulling on the fiber optic cable will not disengage the elements, since the cable is directly attached to a backbone which is coupled only to ferrule holder 12; however, if housing 17 is pulled away from receptacle 10, ramps 19 come into contact with the forward side extensions of latches 16, raising the latches and disengaging hooks 15 from notches 14.
Although the SC design offers several advantages over the ST design, the two connectors are totally incompatible. Moreover, there are already several million ST connectors in use, and this number is quickly approaching ten million. It would, therefore, be desirable and advantageous to devise a push-pull type fiber optic connector having the advantages of the SC connector, but which is fully compatible with the ST design and which could therefore be used on existing ST receptacles.